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RADULA. 



Wm. C. Barbour. 



Radula complanata. Dumort. 



A. Plant natural size. B. Branch with perianth and capsule. C. Leaf 

 with gemmae. Also shows root-hairs from the lower lobe. D. Calyp- 

 tra. E. Spores. 



Radula Dumort. Comm. Bot. 112. 1822. (Martinellius S. F. Gray. 

 Stephanina O. Kuntze.) 



The members of the genus Radula somewhat resemble the Porellas in 

 outward appearance, but are apt to lie more closely upon the substratum of 

 bark, or sometimes rock. 



The plants are rather large, green, and form spreading mats. The stems 

 usually branch in a loosely pinnate manner. The leaves are alternate and 

 incubous in arrangement, the upper margin of each leaf lying over or upon 

 the lower margin of the leaf next above it. As in Frullania and in Porella 

 the leaves are two-lobed, with the lower lobe smaller than the upper, lying 

 beneath it and along the stem at the lower side of the leaf. It may be read- 

 ily distinguished from the other genera with lower lobes smaller than the 

 upper, by the fact that the root-hairs are borne upon the lower lobes of the 

 leaves, while in the others (Frullania, Jubula, Porella, and Lejeunea) they are 

 borne upon the stem and the underleaves. The lobule is seldom much, in- 



